1. Field of the Invention
The present invention relates to a sleeve and an optical connector having the sleeve, which sleeve is put between an optical fiber and a transmitting module or between an optical fiber and a receiving module so as to optically connect the optical fiber and the transmitting or receiving module.
2. Description of the Related Art
An optical connector having a sleeve between an optical fiber and a transmitting module and between an optical fiber and a receiving module is disclosed in Japanese Utility Model Registration Application Laid-open No. 6-33443.
The optical connector has a sleeve having a light-leading path with a constant diameter along an optical axis. Therefore, when a light-receiving surface of the receiving module is smaller than the light-emitting surface of the sleeve, a part of signal light transmitted through the optical fiber cannot be received by the receiving module, thereby lowering the transmission efficiency.
When a light emitting diode (LED) is used as a transmitting module, the light emitted by the light emitting diode diffuses, and a part of the light emitted by the light emitting diode cannot enter the light-leading path of the sleeve.
An optical connector, shown in FIG. 11, disclosed in Japanese Patent Application Laid-open No. 2000-304980 has a higher transmission efficiency of the signal light. The optical connector 102 in FIG. 11 has a receptacle 103 (an equipment-side connector) and a non-shown optical plug to couple the receptacle 103.
The receptacle 103 has a housing 107 of synthetic resin, transmitting and receiving modules 104 and a pair of sleeves 101. The housing 107 is formed in a box-shape and has a pair of accommodating chambers 108 opening in the external wall. And, the housing 107 couples with the optical plug shown in FIG. 11.
The transmitting and receiving modules 104 are accommodated in the respective chambers 108. A pair of sleeves 101 are installed in the housing 107. The sleeve 101 has a light-leading path 126 of frusto-conical shape.
One sleeve 101 is arranged between the optical fiber of the optical plug and the light-emitting surface the transmitting module 104, and the other sleeve 101 is arranged between the other optical fiber of the optical plug and the light-receiving surface of the receiving module 104 in the housing 107. The sleeve 101 is arranged in the housing 107 in a state that the light-leading path 126 reduces its diameter toward the transmitting or receiving module 104.
And, a cap 110 is attached to the housing 107 after accommodating the transmitting and receiving modules 104 in the chambers 108.
The optical plug has a pair of optical fibers, a pair of ferrules, and the plug housing. The pair of optical fibers are arranged in parallel. Each ferrule covers the optical fiber in a state of the end face of the optical fiber being exposed. The plug housing accommodates the ferrule and couples within the housing.
In the optical connector 102, the signal light from the optical fiber proceeds in the light-leading path 126 while making total reflections on the side portion 125 and gathering as approaching the receiving module 104.
On the other hand, when the signal light from the transmitting module 104 is transmitted through the sleeve 101, the light-leading path 126 with the tapered side surface can prevent the light from scattering, thereby improving the transmission efficiency.
With respect to the above prior art optical connector 102, however, since the sleeve 101 is accommodated in the housing 107 in a state that the light-leading path 126 reduces its diameter toward the transmitting or receiving module 104, it is difficult to secure the sleeve 101 in the housing 107 such that the sleeve 101 can optically connect the optical fibers and the respective transmitting and receiving modules 104.
The above structure requires increased man-hours for its assembly work thereby increasing the cost. And also, since the transmitting and receiving modules 104 can not necessarily be optically secured with the optical fibers, the transmission efficiency of the signal light is lowered. Further, the sleeve 101 slips off to an extent of releasing the optical connection.
In view of the foregoing, an object of the present invention is to provide a sleeve and a manufacturing method of the sleeve, wherein the transmission efficiency of the optical connector can be improved and the cost of the optical connector can be reduced with its easier assembly work.
In order to achieve the above object, as a first aspect of the present invention, a sleeve arranged between an optical fiber and a transmitting or receiving module for optically connecting the optical fiber and the transmitting or receiving module comprises: a light-leading path being in a frusto-conical shape having a small-diameter end face facing the transmitting or receiving module; a peripheral projecting portion projecting in a radial direction from another end portion, being on a side of the optical fiber, of the light-leading path; and an outer tube portion extending in an optical axis direction of the light-leading path from a peripheral portion of the peripheral projecting portion toward the small-diameter end face while covering an entire length of the light-leading path.
As a second aspect of the present invention, based on the first aspect, the peripheral projecting portion is circularly formed coaxially with the light-leading path, and the outer tube portion is cylindrically formed coaxially with the light-leading path.
As a third aspect of the present invention, based on the second aspect, an outside diameter of the outer tube portion is substantially uniform over an entire length of the light-leading path.
As a fourth aspect of the present invention, based on the first aspect, the outer tube portion has a flange projecting annularly in a radial direction from a peripheral surface thereof.
As a fifth aspect of the present invention, based on the first aspect, a lens is formed integrally with said another end portion of the light-leading path convexly toward the optical fiber.
As a sixth aspect of the present invention, based on the fifth aspect, the lens does not project over an optical fiber side end of the outer tube portion.
As a seventh aspect of the present invention, based on the first aspect, an end face of said another end portion of the light-leading path is a light-receiving surface to receive light transmitted by the optical fiber, and a diameter of the light-receiving surface is larger than a diameter of a light-emitting surface being an end face of the optical fiber.
As an eighth aspect of the present invention, based on the first aspect, the small-diameter end face of the light-leading path is a light-emitting surface to emit light transmitted to the receiving module, and a diameter of the light-emitting surface is smaller than a diameter of a light-receiving surface of the receiving module.
As a ninth aspect of the present invention, based on any one of the first to sixth aspects, the small-diameter end face of the light-leading path is a light-receiving surface to receive light transmitted from the transmitting module, and a diameter of the light-receiving surface is larger than a diameter of a light-emitting surface of the transmitting module.
As a tenth aspect of the present invention, a method of manufacturing a sleeve arranged between an optical fiber and a transmitting or receiving module for optically connecting the optical fiber and the transmitting or receiving module, wherein the sleeve comprises: a light-leading path being in a flat-headed conic shape having a small-diameter end face facing the transmitting or receiving module; a peripheral projecting portion projecting circularly in a radial direction from another end portion, being on a side of the optical fiber, of the light-leading path; and an outer tube portion extending in an optical axis direction of the light-leading path from a peripheral portion of the peripheral projecting portion toward the small-diameter end face while covering an entire length of the light-leading path, comprising the step of: setting a first metal mold having a first molding portion being along an external shape of said another end portion of the light-leading path of the sleeve and along an external shape of the outer tube portion and a second metal mold having a second molding portion made of hard material and being along an inner surface of the outer tube portion and along a peripheral surface of the light-leading path.
According to the above-described structures of the present invention, the following advantages are provided.
(1) Owing to the peripheral projecting portion and the outer tube portion, the optical connector can be assembled in a state that the sleeve is accommodated and positioned in the mediating pipe of the housing, thereby improving productivity of the optical connector with the sleeve and reducing the cost thereof by reducing man-hour for the assembly work and simplifying the manufacturing process. And, because the outer tube portion extends over the entire length of the light-leading path, the sleeve can be prevented from deflecting in the mediating pipe, thereby improving the transmission efficiency between the sleeve and the optical fiber, the sleeve and the transmitting device, and the sleeve and the receiving device; that is, improving the transmission efficiency of the optical connector with the sleeve.
(2) Because the outer tube portion is coaxially and cylindrically formed similarly to the light-leading path, the sleeve can be securely assembled to the mediating pipe only by accommodating the sleeve into the mediating pipe and can be prevented from deflecting in the mediating pipe, thereby improving productivity of the optical connector with the sleeve, reducing the cost thereof, and improving the transmission efficiency of the optical connector with the sleeve.
(3) Because the outside diameter of the outer tube portion is uniform in a longitudinal direction thereof, the sleeve can be more securely positioned only by accommodating it in the mediating pipe of the housing, thereby improving productivity of the optical connector with the sleeve, reducing the cost thereof, and improving the transmission efficiency of the optical connector with the sleeve.
(4) The flange portion projecting from the peripheral surface of the outer tube portion abuts an inside portion of the housing, the sleeve accommodated in the housing can be more securely positioned, thereby improving the transmission efficiency of the optical connector with the sleeve.
(5) Because an influence of an axial or radial deflection between the optical fiber and the sleeve can be reduced, The transmission efficiency can be improved.
(6) Because the lens does not project beyond the outer tube portion, the lens can be protected by the outer tube portion, thereby facilitating the production management.
(7) Because the diameter of the light-receiving surface of the light-leading path is larger than that of the light-emitting surface of the optical fiber, the light-receiving surface of the light-leading path can receive the light as much as possible, thereby further improving the transmission efficiency.
(8) Because the diameter of the light-emitting surface of the light-leading path is smaller than that of the light-receiving surface of the receiving module, the light-receiving surface of the receiving module can receive the light as much as possible, thereby further improving the transmission efficiency.
(9) Because the diameter of the light-receiving surface of the light-leading path is larger than the light-emitting surface of the transmitting module, the light-receiving surface of the light-leading path can receive the light as much as possible, thereby further improving the transmission efficiency.
(10) Because the second molding portion, formed relatively thin, along the inner surface of the outer tube portion of the second metal mold and the peripheral surface of the light-leading path is made of the hard material, the sleeve can be molded securely. And, owing to the outer tube portion, the optical connector can be assembled in a state that the sleeve is accommodated and positioned in the mediating pipe of the housing. And, because the outer tube portion extends over the entire length of the light-leading path, the sleeve can be prevented from deflecting in the mediating pipe. Therefore, the sleeve enabling the optical connector to reduce the cost and to improve the transmission efficiency can be obtained.
The above and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings.